THURSDAY, Nov. 26, 2015 (HealthDay News) -- Even with regular exercise, people with heart disease who sit too much have worse health than those who sit less, a new study suggests.

Previous research has linked too much sitting with an increased risk of heart disease. But the authors of this study say it's the first to examine the impact of too much sitting on people who already have heart disease.

The study included 278 heart disease patients who had been taught how to increase their exercise levels. For nine days, they wore monitors that recorded their activity levels. The researchers also assessed various indicators of health including body mass index (BMI) and heart-lung fitness.

These heart patients spent an average of eight hours a day sitting, the study found. On average, men sat an hour more daily than women, mostly because women engaged in more light intensity activity such as housework or running errands.

Patients who spent more time sitting had a higher BMI and lower heart-lung fitness, according to the study published Nov. 26 in the European Journal of Cardiovascular Prevention. BMI is an estimate of body fat based on height and weight.

"These relationships remained even when we controlled for an individual's age, gender or physical activity levels. In other words, people who sat for longer periods were heavier and less fit regardless of how much they exercised," said lead author Stephanie Prince, a post-doctorate fellow in the division of prevention and rehabilitation at the University of Ottawa Heart Institute, in Canada.

"Women with coronary artery disease spend less time sitting for long periods but we need to do more research to understand why," she said in a journal news release. "There is some research from the past which suggests that at around the age of 60 men become more sedentary than women and may watch more TV."

Some easy ways to get some activity include getting up and moving every 30 minutes. The researchers also suggest standing up during TV commercials or doing light exercises while watching TV, or taking regular breaks from your desk.

However, Prince emphasized that sitting less is not a replacement for exercise.

"It's important to limit prolonged bouts of sitting and in addition to be physically active," she said. "Sedentary time may be another area of focus for cardiac rehabilitation programs along with exercise."